Upgrade the Orion in the following fashion:
1) Rip out it's reactor, replace it with a Vasudan one. Maybe the ones that go on the Hetasphut or something.
2) Change all beam cannons to their Vasudan counter parts. (Bvas, Vslash)
3) replace the "Terran Turrets" with more flak and perhaps some M-S, Maxims, or even subachs
4) Add some more anti-fighter beams.
Depending on the cost, I would also use that handy collapsed core molybdenum (which would be an increase in HP)
For the Hecate, simply again replace ll beam cannons to their Vasudan counterparts, and replace the forward slasher with an Bvas.
Deploy the Hecates with Orions. The Hecates provide fighter cover, Orions punch holes. add a liberal amount of Deimoses for escort, and perhaps if you can get production up and running again, Aeoluses.
Deimos: Perhaps replace the slashers with small Vasudan beams? Also, considering the larger borders the GTVA has, perhaps add a small hangar bay on it, decrease the speed, and call in a "patrol Corvette" designed to work far from GTVA battlegroups.